This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 from an application for SENSOR FOR DETECTING WATER LEVEL earlier filed in the Korean Industrial Property Office on Jul. 13, 2001 and there duly assigned Serial No. 2001-42375.
1. Field of the Invention
The present invention relates generally to water level sensors, and more particularly to a water level sensor for sensing water levels by detecting the electric conductivity of water using reference and measuring electrodes.
2. Description of the Prior Art
In general, a water level sensor used for washing machines serves to sense the water levels of washing water supplied to the water tub of a washing machine. In most cases, the water levels are sensed using a mechanical switch or LC oscillation technique.
Of those methods, the LC oscillation technique, as shown in FIG. 1, is performed in such a manner that a water level sensor is positioned in the space between a water tub 1 and a spin-drying tub 2, a water level sensor generates a water level signal corresponding to the variation of air pressure according to the amount of washing water and inputs the signal to a microprocessor, and the microprocessor senses the water level of the washing water on the basis on a water level detection signal.
However, the water level sensor employing the mechanical switch fails to precisely measure the water level of washing water since the water level is measured on the basis of water pressure generated by washing water supplied to the water tub. The water level sensor employing the LC oscillation technique fails to precisely measure the water level of washing water because of errors due to the variations of an outdoor temperature and long-term wear and tear.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a water level sensor that is capable of detecting water levels using reference and measuring electrodes embedded in a water tub.
In order to accomplish the above object, the present invention provides a water level sensor for measuring a water level of a water tub, comprising: a reference electrode comprised of a plurality of electrode plates to detect electric conductivity of water filling a space between the electrode plates of the reference electrode; and a measuring electrode comprised of a plurality of electrode plates extended along a length of the water tub to be longer than the electrode plates of the reference electrode and spaced apart from the electrode plates of the reference electrode to detect electric conductivity of water filling a space between the electrode plates of the measuring electrode.
Preferably, the reference electrode may provide a detection value as a reference value for water level detection, the measuring electrode provides another detection value as a measured value corresponding to a contact area between water and the electrodes varying according to water levels, and the water level is calculated by a difference between the reference and measured values.
Preferably, the electrodes may be embedded in the water tub to allow the surfaces thereof to be exposed to the interior of the water tub.
Preferably, the electrodes may be plated with metal to form metallic coatings on the surfaces thereof.
Preferably, the water level sensor may be applied to a washing machine, water purifier or humidifier.